A. Field of the Invention
The present invention relates to a clutch operating mechanism, and more particularly to a clutch operating mechanism used with a clutch disk, clutch cover and pressure plate, where the clutch operating mechanism produces force which urges the pressure plate into engagement with the clutch disk and a flywheel of an associated engine.
B. Description of Related Art
A conventional clutch mechanism usually includes a clutch disc, a clutch cover assembly and an actuating mechanism.
The clutch disc typically includes friction surfaces, a plate member that is coupled to and supports the friction surfaces and a spline hub elastically coupled to the plate member. Usually, the elastic coupling between the spline hub and the plate member includes a spring for dampening unwanted vibrations produced during the transmission of torque. An input shaft that extends from a transmission usually extends through the spline hub.
The clutch cover assembly usually includes a clutch cover connected to the flywheel of the engine, an annular pressure plate disposed within the clutch cover, and a diaphragm spring. The clutch cover and pressure plate confine and engage the clutch disk between the pressure plate and a flywheel.
The release mechanism is provided with a release bearing which engages an inner circumferential edge of the diaphragm spring. A drive mechanism connected to the release mechanism provides control for moving the release bearing in axial directions to move the diaphragm spring. In the case where the drive mechanism includes, for example, a hydraulic cylinder, the hydraulic cylinder is connected to a master cylinder. When a driver or operator manipulates a switch or lever, hydraulic fluid is forced from the master cylinder to the hydraulic cylinder. As a result, a piston within the hydraulic cylinder is moved in a predetermined axial direction so that the release bearing is also moved in the axial direction. The release bearing causes the inner circumferential edge of the diaphragm spring to move, so that the biasing force from the diaphragm spring to the pressure plate is released. As a result, the clutch is disengaged.
In the above-described clutch device, the movement of the piston works against the force or pressure from the diaphragm spring. As the diaphragm spring is moved, it is necessary to simultaneously control the load from the piston imparted to the release bearing that works against the force of the spring and control the distance the diaphragm spring moves. The distance the diaphragm spring is often referred to as the displacement of the diaphragm spring or stroke of the diaphragm spring. Since both force and stroke must be controlled, the structure of the control section is complicated, otherwise the reliability of the clutch control may be compromised. Also, since the spring characteristics of the diaphragm spring affect the pressure load, the reliability of the clutch control may be further compromised.
An object of the present invention is to enhance the reliability of a clutch control in a clutch device.
In accordance with a first aspect of the present invention, a clutch mechanism includes a clutch cover and an annular pressure plate disposed within the clutch cover and attached to a radially outward portion thereof for limited axial movement with respect to the clutch cover, the annular pressure plate having a pressure surface engageable with a friction face of a clutch disk. An annular lever plate is supported at an outer circumferential edge of the clutch cover, the annular lever plate being in contact with the annular pressure plate radially inward from the outer circumferential edge of the clutch cover. The annular pressure plate is biased away from engagement with the clutch disk.
Preferably, the clutch cover includes a plurality of strap plates attached to a radially outward portion thereof, the strap plates further connected to a radially outward portion of the annular pressure plate.
Preferably, the strap plates are configured to bias the annular pressure plate away from the clutch disk.
Preferably, the strap plates and the annular lever plate are both configured to bias the annular pressure plate away from the clutch disk.
Preferably, a bearing assembly is disposed adjacent to the annular pressure plate and supported about a transmission input shaft for axial movement along the input shaft, a portion of the bearing assembly configured to contact an inner circumferential edge of the lever plate. A hydraulic drive mechanism is connected to the bearing for effecting movement of the bearing.
Preferably, the lever plate is formed with a plurality of first slits extending radially inwardly from an outer circumferential edge thereof and a plurality of second slits extending radially outwardly from an inner circumferential edge thereof in an alternating manner.
Alternatively, a pneumatic drive mechanism may be employed for effecting movement of the bearing.
In accordance with another aspect of the present invention, the clutch mechanism includes a clutch cover having a plurality of strap plates attached to a radially outward portion thereof and an annular pressure plate disposed within the clutch cover and attached to the strap plate for limited axial movement with respect to the clutch cover, the annular pressure plate having a pressure surface engageable with a friction face of a clutch disk. An annular lever plate is supported at an outer circumferential edge of the clutch cover, the annular lever plate being in contact with the annular pressure plate radially inward from the outer circumferential edge of the clutch cover. The annular pressure plate is biased away from engagement with the clutch disk by the strap plates.
Preferably, the strap plates are configured to bias the annular pressure plate away from the clutch disk and the annular lever plate is formed with a plurality of first slits extending radially inwardly from an outer circumferential edge thereof and a plurality of second slits extending radially outwardly from an inner circumferential edge thereof in an alternating manner such that biasing effects of the annular lever plate are less than the strap plates.
Preferably, the strap plates and the annular lever plate are configured to bias the annular pressure plate away from the clutch disk.
In another aspect of the invention, a clutch mechanism includes a clutch cover having a plurality of strap plates attached to a radially outward portion thereof and an annular pressure plate disposed within the clutch cover and attached to the strap plate for limited axial movement with respect to the clutch cover, the annular pressure plate having a pressure surface engageable with a friction face of a clutch disk. An annular lever plate is supported at an outer circumferential edge of the clutch cover, the annular lever plate being in contact with the annular pressure plate radially inward from the outer circumferential edge of the clutch cover. The annular pressure plate is biased away from engagement with the clutch disk by the strap plates and the annular lever plate.
Preferably, the annular lever plate is formed with a plurality of first slits extending radially inwardly from an outer circumferential edge thereof and a plurality of second slits extending radially outwardly from an inner circumferential edge thereof in an alternating manner.
Preferably, the annular lever plate has a length R5 measured from an inner circumferential edge to an outer circumferential edge thereof, the first slits have a radial length R3 and the second slits have a radial length R4 such that the radial lengths R3 and R4 are approximately 80% of the length R5.
In the clutch mechanism according to the one aspect of the invention, when the bearing is moved toward the flywheel by the drive mechanism, the annular lever plate is deformed along the outer circumferential edge thereof as a fulcrum so that a radially intermediate portion thereof presses the pressure plate toward the flywheel. As a result, the pressure surface of the pressure plate causes the friction surface of the clutch disc to frictionally engage with the flywheel. In this case, a load which is several times larger than a load from the bearing to the inner circumferential edge of the diaphragm spring is applied to the pressure plate, corresponding to a ratio (lever ratio) of a length from the inner circumferential edge of the lever plate to the outer circumferential edge thereof to a length from the outer circumferential edge to the radially intermediate portion.
When the bearing returns to a position toward the transmission by release of fluid pressure by the drive mechanism, the force transmitted by the annular lever plate to the pressure plate is overcome by the force of the strap plates and thus, the clutch is disengaged.
In this clutch mechanism, a conventional diaphragm spring is not used for biasing the pressure plate. The pressure transmitted from the lever plate to the pressure plate is provided only by movement of the bearing against the inner circumferential edge of the annular lever plate. Thus, it is possible to control the clutch mechanism only by controlling the position of the bearing. The forces normally associated with a diaphragm spring are eliminated thus reducing the force required to operate the clutch mechanism. Further, the lever action of the annular lever mechanism multiplies the force from the bearing against the pressure plate, thus further reducing the force necessary to control engagement and disengagement of the clutch mechanism. Therefore, the reliability of the clutch control is enhanced.
In the clutch mechanism according to the present invention, since the first slits and second slits are formed in the lever plate, the lever plate has only the minimal rigidity.